1. Field of the Invention
The present application concerns methods to improve the quality of injection molded optical components.
2. Description of Related Art
Currently, even xe2x80x9coptimumxe2x80x9d conditions for injection molding silicone lenses and other optical components including intraocular lenses, and soft contact lenses, produces an unacceptably high number of lenses with optical defects. These defects originate from areas of resin that polymerizes (xe2x80x9ccuresxe2x80x9d) at a different rate than the bulk of the resin making up the lens. This problem of xe2x80x9cpre-curingxe2x80x9d is related to resin residue that sticks to the various parts of the injection apparatus. This problem also appears to be due to buildup of a static charge within the resin mass. In any case, regular or haphazard cleaning methods fail to alleviate this problem. Through careful experimentation I have developed a protocol that specifies the conditions and steps to rid an injection system of impurities and static charge.
The present method for improving the quality of injection molded optical components consists of proper cleaning of the injection molding apparatus between uses. Injection parts that are not subjected to pressurized polymer are cleaned by passage through a series of isopropyl alcohol baths. At each stage clean brushes are used to remove any contaminating polymer. Those injection parts that are subjected to pressurized polymer are best passivated by a succession of thermal cycles in isopropyl alcohol. Thermal cycling removes a contaminant or charge that promotes pre-curing of polymer during the injection process.